Lens Terminology

Focal Length

Focal length is the distance between the camera sensor and the
center of the lens. The greater the focal length, the larger the
image will appear. Therefore, the greater the focal length, the
more the lens becomes telephoto in application.

F# / F-Stop

The f/number is an indication of the brightness of the lens. It is
the measurement of the ratio between the focal length and the diameter
of the entrance pupil (where the light enters the lens). The f/number is
directly proportional to the focal length and inversely proportional to
the effective diameter of the lens. It determines the amount of light
reaching the camera sensor. The smaller the value, the larger the
opening and the brighter the image produced by the lens.

Minimum Object Distance

The Minimum Object Distance indicates how close the lens can be
placed to the object for shooting. It is measured from the vertex of the
front glass of the lens.

Lens Mount

1) Any camera may use a lens equal
or greater than the format of the sensor. For example, a 1/2" format
camera may use a 2/3" format lens.
2) F-mount lenses are compatible with C-mount cameras. An F-To-C mount
converter is required to use F-mount lenses with C-mount cameras,see lens accessories.
3) F-mount lenses are compatible with CS-mount cameras. A 5mm extension
tube (C-To-CS mount converter) and F-To-C mount converter are required
to use F-mount lenses with C-mount cameras, see lens accessories.